NFC Tag Frontend Circuit Phase Calibration Method
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Solution Overview
Problem
Current NFC tag devices require laborious and time-consuming phase calibration processes to achieve the correct phase difference for active load modulation, which is essential for efficient communication, but these processes are not suitable for high-volume production due to their lengthy duration.
Innovation Solution
A method for phase calibration within the frontend circuit of an NFC tag device that automatically adjusts the phase difference of the active load modulation signal with respect to the reference signal, allowing for rapid determination of the optimal phase setting, significantly reducing calibration time to approximately one millisecond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual phase calibration methods are used to achieve correct phase difference for active load modulation, then communication efficiency is improved, but calibration time becomes excessively long and productivity decreases
Solution Approach 1:
The frontend circuit performs phase calibration autonomously by measuring the test signal amplitude at its own antenna and automatically adjusting the phase difference of the active load modulation signal. This self-service calibration eliminates the need for external manual calibration equipment and procedures, significantly reducing calibration time while maintaining communication efficiency.
Solution Approach 2:
The calibration method employs feedback by measuring the amplitude of the test signal (which results from overlaying the reference signal with the active load modulation signal) and using this measurement to determine the optimal phase difference setting. This feedback mechanism enables automatic phase adjustment without manual intervention.
2Productivity
If automated phase calibration is implemented within the frontend circuit, then calibration time is reduced to approximately one millisecond, but device complexity increases
Solution Approach 1:
The frontend circuit is designed to perform multiple functions: it generates the active load modulation signal, measures the test signal amplitude at its antenna, and automatically adjusts the phase difference for calibration. By making the frontend circuit multi-functional, the patent avoids adding separate calibration hardware, thus limiting the increase in device complexity while achieving rapid calibration.
3Measurement precision
If phase calibration is performed manually with external equipment, then measurement precision can be ensured, but the process becomes laborious and time-consuming
Solution Approach 1:
The frontend circuit performs self-calibration by measuring the test signal amplitude at its own antenna and automatically determining the optimal phase difference setting. This eliminates the need for external calibration equipment and manual procedures, reducing calibration duration from minutes to approximately one millisecond while maintaining measurement precision through automated amplitude-based phase determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables rapid and efficient phase calibration, reducing the overall calibration time and making it feasible for high-volume production by automating the phase setting process within the frontend circuit of NFC tag devices.
Implementation Method 1
NFC tag devices are employed in Radio Frequency Identification (RFID) systems that allow communication between an NFC tag device and a corresponding NFC reader device using inductive coupling
Implementation Method 2
The tag device, which is also called a transponder, transmits data to the reader using signals with a frequency which is an integer divider of the carrier frequency, e.g., 13.56 MHz/16 and is named the subcarrier frequency. According to ISO/IEC 14443, the transponder is powered by the field of the reader and applies a load modulation to the reader's signal when transmitting data
Implementation Method 3
An amplitude of a test signal present at an antenna of the NFC tag device is measured. The test signal results from overlaying of the reference signal with the active load modulation signal
Data Source
AI summary
A method for a phase calibration in a frontend circuit of a near field communication (NFC) tag device is disclosed. An active load modulation signal is generated with a preconfigured value of a phase difference with respect to a reference signal of an NFC signal generator device. An amplitude of a test signal present at an antenna of the NFC tag device is measured. The test signal results from overlaying of the reference signal with the active load modulation signal. The following steps are repeated: modifying the value of the phase difference, providing the active load modulation signal with the modified value of the phase difference, measuring an amplitude of the test signal and comparing the measured amplitude with the previously measured amplitude until the measured amplitude fulfills a predefined condition. The value of the phase difference corresponding to the previously measured amplitude is stored.